Various strategies are known for increasing the amount of power that a gas turbine engine may be able to produce. One method of increasing the power output of a gas turbine engine is by cooling the inlet air before compressing it in the compressor. Such cooling causes the air to have a higher density so as to create a higher mass flow rate into the compressor. The higher mass flow rate of the air in a compressor allows more air to be compressed so as to allow the gas turbine engine to produce more power. Additionally, cooling the inlet air temperature increases the overall efficiency of the gas turbine engine.
Given such, fogging systems may be used about a compressor inlet section so as to provide a stream of water droplets to cool the incoming flow of air. The fogging system generally may be controlled by the humidity of the incoming flow of air. For example, humility sensors and temperature sensors may be positioned about the compressor inlet so as to measure the humidity of the incoming flow. Based on the readings of the humidity and temperature, the fogging system may calculate how much water can be evaporated and may inject such an amount into the flow of air. Drawbacks with such a fogging system, however, include the facts that not all of the water evaporates, that there may be insufficient residence time for the water to evaporate, that the water droplets tend to agglomerate, and that these water droplets may form projectiles that can hit the compressor blades so as to cause pitting and other types of damage. Localized temperature depressions also may cause water to drop out of the airstream and cause erosion.
There is thus a desire for an improved control system for an inlet fogging system or other type of inlet air cooling system for use with a gas turbine engine. Preferably such a system, based on real time measurements, can control the size of the water droplets and the amount of water injected in the incoming flow of air so as to avoid damage to the compressor blades while promoting overall turbine efficiency and power output.